Pure water freezes at 32° F, but a 60% solution of DOWFROST propylene glycol pushes the freezing point down to -60° F. While the freezing point of pure glycol is only -39° F, the synergy between glycol and water results in a much lower freezing point. This is very important for closed-loop systems that may be exposed to freezing conditions.
What is the difference between freeze protection and burst protection? As the temperature of the water-glycol solution falls, the water will begin to freeze and “precipitate” out of the solution, causing the fluid to become slushy. Most systems can handle short periods of slush if the viscosity remains low. The “slush” period is termed burst protection. As the temperature continues to decrease, the glycol begins to freeze. Unlike water, which expands when it freezes, glycol contracts when it freezes. Therefore, when the glycol freezes, the volume in the system actually decreases. With freeze protection, there will not be any freezing of water or glycol in the mixture.
Relying on DOWFROST propylene glycol in your closed-loop water system means you’re relying on the best freeze protection possible. DOWFROST Heat Transfer Fluid is the only inhibited glycol made with DOW PuraGuard Propylene Glycol USP/EP, a pharmaceutical grade of monopropylene glycol with specified purity greater than 99.8%. By contrast, competitor products are often made from recycled or industrial grade glycols or from glycols derived from bio-renewable sources. These glycols typically do not meet USP specifications, as they contain significant amounts of impurities like ethylene glycol or diethylene glycol, which at certain levels affect toxicity. They also may contain certain other impurities, such as dioxolanes, which impart strong odors and cause excessive foam. A great way to prolong fluid lifetime and to lower your cost of ownership is to use DOWFROST heat-transfer fluid, because it’s made with the highest industry purity propylene glycol combined with long-lasting and food-safe corrosion inhibitors.